The present invention relates to a coating varnish composition and an antifouling coating composition to be used for preventing attachment of marine organisms to the underwater or submarine structures such as ships, fishing nets, drainage conduits, etc.
Numerous species of marine organisms, such as barnacle, ascidian, serpula, mussel, laver, etc., live in the seawater. When a structure such as a ship, fishing net, drainage pipe, etc., is set or placed in commission in or on the sea, the marine organisms cling to the structure and grow to give various kinds of damage to the structure. For instance, if the ship's bottom is incrusted with marine organisms, the frictional resistance of the seawater increases to cause a reduction of cruising performance of the ship, so that if it is tried to keep a constant cruising speed of the ship, its fuel consumption increases to pose a serious economical problem. Also, if the marine organisms cling to the fishing nets used for ocean culture, the meshes of the nets would be clogged up, which could prove fatal to the cultured fishes and shellfishes.
Hitherto, in order to prevent attachment of the marine organisms to the underwater structures such as mentioned above, the antifouling paints using homopolymers or copolymers of organotin-containing unsaturated monomers as resinous component (see Japanese Patent Examined Publication (JP-B)-40-21426, JP-B-44-9579, JP-B-46-13392, JP-B-49-20491, JP-B-51-11647, JP-B51-12049, JP-B-52-48170, etc.) have been applied on said structures. These polymers have their organotin portion hydrolyzed with the seawater (pH: 8.0-8.3). As a result, not only the organotin serves as an antifouling agent, but also the polymer surface which has been made soluble in seawater is gradually corroded by the moving sea water to bare out the new coating surface, thus producing a long-lasting stabilized antifouling effect. However, the organotin released into the seawater from the paints is hard to decompose and may be taken in by and accumulated in the marine organisms and, through the food chain, it may get into the human system. This involves the possibility of causing serious physical troubles such as deformity. So, use of the organotin compounds has been limited by law.
Request is now voiced in the art for the development of a resin for antifouling paints which is capable of producing a long-lasting stabilized antifouling effect, in place of the organotin-based resins which involve such a high order of danger. Ideally speaking, it is desirable that the resins used for antifouling paints are of a hydrolyzable type and show a pertinent coating consuming property like the organotin-based resins, but proposals involving use of hydrophilic or water-repellent resins have also been made (Japanese Patent Unexamined Publication (JP-A)-62-290768, JP-A-62-13471, JP-A-58-180565, JP-A-57-67672, etc.). However, it is hardly possible to realize a long-lasting stabilized antifouling effect by use of a resin having the hydrophilic or water-repellent property alone.
In view of the above, various hydrolyzable resins having a specific carboxylic acid ester in the side chain have been proposed (WO 84/02915, JP-A-2-69576, JP-A-63-215780, JP-B-55-39271, JP-A-62-57464, JP-B-61-3830, etc.), but their effect has not been well satisfactory.
On the other hand, JP-A-2-99567 proposes use of a copolymer of a maleic anhydride derivative for said purpose. This copolymer has no toxicity different from the organotin-based resins and can be expected to be excellent in coating consuming properties. However, this polymer, in use for an antifouling coating composition, had a serious defect in that it might cause thickening-gelation of the composition as it is mixed with a copper compound which is currently used as a poisonous substance.
Use of a triazole derivative for the purpose of preventing such thickening-gelation in the case of a composition comprising a polymer having a triorganotin group is reported (JP-A-57-92061). However, in case of using a polymer having a triorganotin group as base material, addition of a triazole derivative is of little avail, and it is impossible to obtain a good coating composition and to form a good coating.